This invention relates generally to the formation of positive resist masks using high energy radiation and more particularly to the solvent development of electron irradiated acrylate polymer resist layers.
The formation of positive resist masks from layers of radiation degradable polymers is described, for example, by Haller and Hatzakis in U.S. Pat. No. 3,535,137. A radiation degradable polymer layer is coated on a substrate and is subjected to patternwise exposure by high energy radiation such as, for example, x-rays, nuclear radiation, and electrons. The irradiated regions of the polymer suffer a decrease in molecular weight and therefore become more rapidly soluble. A developer is then used to preferentially remove the irradiated portions of the layer. The substrate is then subjected to an additive or substractive process such as metallization or etching with the remaining portions of the resist layer acting to protect the substrate.
Although it is possible to employ developers which attack only the radiation exposed portions of the resist layer and which leave the unexposed portions almost intact, it has been found that higher process speeds can be obtained if a solvent is employed which attacks both the exposed and unexposed portions of the resist layer but which attacks the exposed portion at a higher rate. In order to further speed up the resist mask formation process, developing techniques which speed the development of exposed portions of the resist particularly when using higher molecular weight materials are desirable.